continuing from google search hit 4:
"According to numerous studies, increasing the outdoor air 350 - 390-ppm CO2 content in the Greenhouse to around 1,000 ppm increases the crop production about 30 - 50 %.

The automatic ASCO2 System is an ideal solution for greenhouses in need of CO2 - enriched climate. With no emissions of contaminating by-products, the ASCO2 solution guarantees a productive and healthy climate for the plants and good control of mold/fungi spores and pesticides.

As the system does not produce CO2, but only absorbs it from the atmosphere and later releases it into the greenhouse, it is a very environmentally friendly technology, which can help you in creating a favorable image for your products.

The costs of producing CO2 using the ASCO2 system are far below the price of CO2 in the market. In addition to electricity costs, there are no material or fuel costs related to the CO2 solution. The ASCO2 Carbon Dioxide Absorbent service life is well over 5,000 recovery cycles, which means years of almost maintenance-free operation. And there is no need to continue carrying the CO2 bottles nor fuels or raw materials to the Greenhouse."
http://www.casavonen.com/en/CO2-Greenhouses.htm